Skip starting sync service on watchdog when receiving disabled

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -2012,6 +2012,9 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
     }
 
     static void watchdog(Context context) {
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        boolean enabled = prefs.getBoolean("enabled", true);
+        if (enabled)
             start(context,
                     new Intent(context, ServiceSynchronize.class)
                             .setAction("watchdog"));